Noah Baumbach has found a muse in Greta Gerwig. A kooky blonde with the spirit of Goldie Hawn and the mannerisms of Diane Keaton, she is the Keaton to his Allen, the Cruz to his Almodóvar. She fits his casually observational style so well that it’s a wonder she’s only taken part in three of his films: they’re dexterously able to finish each other’s cinematic sentences like an old married couple. So I suppose it’s no surprise that Gerwig co-wrote their most recent two collaborations (Frances Ha, Mistress America), and it’s no surprise that the duo has been in a personal relationship ever since they completed their initial partnership. They’re made for each other, professionally, and, as it seems, personally.

In a role that could have perhaps made her a bona fide star had Mistress America been a wide release instead of an indie gem, Gerwig ebulliently portrays Brooke Cardinas, a free spirit in her late twenties with a personality that could kill. Aimless but somehow infectiously confident in an unforgiving New York City, she is called upon by Tracy Fishko (Lola Kirke), an eighteen-year-old struggling to adjust to college life in the city. As Tracy’s mom and Brooke’s dad are getting married in a few months, Tracy figures it wouldn’t hurt to get to know her soon-to-be stepsister.

Being previously lonely and plagued with immense boredom, the decision proves to be life-changing. Basically taking her under her wing, Brooke becomes Tracy’s guiding light and stand-in best friend, the cool gal pal you always wanted to have but never really got to experience for yourself. Misadventures around the city ensue, and Tracy has the time of her life. But, being an aspiring writer, she makes the not-so-wise decision to write about and potentially publish a story revolving around her exploits with Brooke, which paints the young woman in a less-than-ideal light.

Throughout Mistress America, we find ourselves having such a great time that it comes as something of a shock that it isn’t shy when it comes to jumping into the heavy too. When it does, we grow to appreciate just how accomplished Baumbach and Gerwig’s writing is, and how appealing, and how authentically drawn, the performers are. I like how none of the characters are conventionally likable — Tracy takes herself too seriously and is maybe even a little sociopathic; Brooke a person that, as one person in the film describes, is the type who is able to see everyone else through clear eyes but not herself — and I like that the screenplay is aware of its characters’ intellectuality but sees through them almost immediately. Mistress America is not the atypical screwball comedy — it’s too human for that — but it glows with wit, speed, and soft pragmatism. B+